1. Field of the Invention
The present invention relates to ducted fans. More particularly, the present invention relates to a ducted spinner for engine cooling in an aircraft, such as a ducted fan aircraft.
2. Background Information
In many conventional ducted fan aircraft, such as vertical takeoff and landing (VTOL) ducted fan aircraft, there is a need to have a relatively bulky air cooled engine in very close proximity to the fan rotor. While the propulsion fan provides a very high airflow speed past the engine, there are significant thrust losses involved. In conventional air cooled engine installations, the engine drives a propeller that produces significantly lower air speeds, so the losses are much less critical. In addition, for minimizing the drag, it is desirable to use a smoothly diverging duct between the cooling air inlet scoops and the engine. The duct decelerates the high speed external air flow down to the appropriate speed to pass it through the engine fins.
However, for ducted fan propulsion systems, there is very little length between the fan and the engine to install such a duct. Making the duct short enough to fit will result in separated airflow and very high drag losses. In some cases, a long crankshaft is used to provide more spacing between the fan and the engine. However, such a configuration adds weight to the system, and, in many cases, also results in an increase in the duct length, which adds even more weight.